From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM
	autolearn=unavailable autolearn_force=no version=3.4.4
X-Received: by 10.107.183.193 with SMTP id
 h184mr17081145iof.129.1511538769289;
        Fri, 24 Nov 2017 07:52:49 -0800 (PST)
X-Received: by 10.157.81.193 with SMTP id d1mr1210922oth.13.1511538769154;
 Fri, 24 Nov 2017 07:52:49 -0800 (PST)
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!news.stack.nl!usenet-its.stanford.edu!usenet.stanford.edu!i6no5402252itb.0!news-out.google.com!x87ni3369ita.0!nntp.google.com!d140no5407507itd.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail
Newsgroups: comp.lang.ada
Date: Fri, 24 Nov 2017 07:52:48 -0800 (PST)
In-Reply-To: <ov93ij$njh$1@dont-email.me>
Complaints-To: groups-abuse@google.com
Injection-Info: glegroupsg2000goo.googlegroups.com;
 posting-host=2003:c7:83c9:d68a:40e3:26f3:2b96:8cea;
 posting-account=rmHyLAoAAADSQmMWJF0a_815Fdd96RDf
NNTP-Posting-Host: 2003:c7:83c9:d68a:40e3:26f3:2b96:8cea
References: <d8c0ce45-97ad-4475-b3f9-1662a875a576@googlegroups.com>
 <ov93ij$njh$1@dont-email.me>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <3f2c41db-3944-4b37-99b8-b71d55d5f8ed@googlegroups.com>
Subject: Re: How to access an array using two different indexing schemes
From: AdaMagica <christ-usch.grein@t-online.de>
Injection-Date: Fri, 24 Nov 2017 15:52:49 +0000
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Xref: feeder.eternal-september.org comp.lang.ada:48176
Date: 2017-11-24T07:52:48-08:00
List-Id: <comp.lang.ada>

Am Freitag, 24. November 2017 13:33:25 UTC+1 schrieb Jeffrey R. Carter:
> On 11/24/2017 12:42 PM, Jerry wrote:
> > I want to access an array such as Real_Vector (built-in for Ada >=3D 20=
05) with two different indexing schemes. For example, I would access a Real=
_Vector indexed (0 .. 4) when thinking of it as a times series and the same=
 data indexed (1 .. 5) when thinking of it as a vector. Another application=
 would be a vector indexed (-128 .. 127) because it fits my problem domain,=
 perhaps a spatial variable, but I need to index it as (0 .. 255) when thin=
king of doing a Fast Fourier Transform on it.
>=20
> I can't think of any situation when I'd need to access the same component=
 of an=20
> array using different indices, but I note that this compiles:
>=20
> procedure Renaming is
>     subtype T1 is String (1 .. 5);
>     subtype T2 is String (2 .. T1'Length + 1);
>=20
>     S1 : T1 :=3D "Hello";
>     S2 : T2 renames S1;
> begin -- Renaming
>     null;
> end Renaming;

  procedure Renaming is
    subtype T1 is String (1 .. 5);
    subtype T2 is String (1 .. 0);   -- !
    S1 : T1 :=3D "Hello";
    S2 : T2 renames S1;
  begin -- Renaming
    Put (S1'First'Image); Put (S1 (S1'First));
    Put (S2'First'Image); Put (S2 (S2'First));
    Put (S1'Last 'Image); Put (S1 (S1'Last ));
    Put (S2'Last 'Image); Put (S2 (S2'Last )); New_Line;
  end Renaming;

This results in
 1H 1H 5o 5o

Rememner that renamings ignore constraints.